Mechanical devices, such as internal combustion engines, require the use of a lubricant to protect mechanical parts from wear, to promote friction reduction, to inhibit rust and the like. Indeed, today automotive engines are designed to operate at higher temperatures than in even the recent past and these higher operating temperatures require higher quality lubricants.
One of the requirements for lubricants for use in currently designed engines is for higher viscosity indices (VI's) in order to reduce the effects of the higher operating temperatures on the viscosity of the engine lubricants.
Poly alpha olefins (PAO's) produced by polymerizing linear alpha olefins, especially C8 to C12 linear alpha olefins have excellent VI's and consequently have found use as lubricant base oils. Unfortunately, linear alpha olefins are expensive and often in short supply, thereby limiting the use of PAO's in lubricant compositions. Therefore, there is a need for synthetic base oils that are less expensive than PAO's and that have equivalent or better properties.
Olefins such as ethylene, propylene and butene are available in large quantities at relatively low cost. Thus, producing base oils from these nonomers offers the potential as a low cost alternative to PAO's. Attempts to form base oils by copolymerizing ethylene with an alpha olefin having at least 3 carbon atoms has not led to entirely satisfactory products. Typically, liquid ethylene/alpha olefin copolymers have poor pour points and cloud points, and are often hazy.
Thus, there remains a need for synthetic base stocks that have high VI's, e.g., greater than about 110 and good low temperature properties such as pour point, cloud point and are haze-free.